1. Field of the Invention
The present invention relates to an axle driving apparatus, whose output speed is changed by manipulation of a traveling control member, wherein the human operational force to be applied onto the traveling control member can be reduced.
2. Background Art
Conventionally, there is a well-known axle driving apparatus having a construction such that a hydraulic pump driven by an engine, a hydraulic motor fluidly connected with the hydraulic pump and an axle driven by output rotation of the hydraulic motor are incorporated in a common housing. Hereinafter, such an axle driving apparatus is referred to as an integrated hydraulic transmission, namely, an “IHT”. Also, hereinafter, a hydrostatic transmission constituted by the hydraulic pump and the hydraulic motor fluidly connected with each other is referred to as an “HST”.
At least either the hydraulic pump or the hydraulic motor is of a variable displacement type provided with a capacity changing device like a movable swash plate in connection with a human-operated traveling control member. The capacity thereof is continuously varied according to the operational degree of the traveling control member so as to continuously change the rotational speed of the axle.
The IHT is lightened and compacted because the hydraulic pump, the hydraulic motor and the axle are incorporated together in the common housing, thereby being advantageous in compacting a vehicle equipped with the IHT. However, if the vehicle travels with the axles under a heavy load, an operator is troubled to apply great force onto the traveling control member for the speed changing operation, thereby hindering a smooth speed changing.